The present invention relates to a spark-ignition direct injection engine.
Arts that achieve both improvements in exhaust emission performance and thermal efficiency have been known, for example, U.S. Pat. No. 7,121,233B2 (JP2004-316544A) discloses an engine having a combustion mode of igniting mixture gas inside a cylinder by compression. For such compression-ignition combustion, it is required to increase the in-cylinder temperature so as to increase ignitability and stability.
However, with engines performing a fuel cut in deceleration, there have been cases where the in-cylinder temperature decreases during the fuel cut, and when the fuel supply is resumed, the in-cylinder temperature has lowered to the extent where compression ignition is difficult to perform.
Thus, with the engine disclosed in U.S. Pat. No. 7,121,233B2 (JP2004-316544A), when resuming from the fuel cut, spark-ignition combustion for increasing the in-cylinder temperature is performed before the compression-ignition combustion.
Moreover, an in-cylinder temperature decrease due to a fuel cut causes a disadvantage also in view of activating a catalyst.
In this regard, with the method using the engine disclosed in U.S. Pat. No. 7,121,233B2 (JP2004-316544A), the in-cylinder temperature can be increased promptly when resuming from the fuel cut; however, the in-cylinder temperature still decreases once due to the fuel cut. As a result, the temperature of the catalyst also decreases once.